This invention pertains to the preparation of stable, aqueous colloidal dispersions of carboxylic acid or sulfonic acid-containing vinyl resins and more particularly to their preparation of vinyl resin colloidal dispersions by mixing said resins with water, base, an organic solvent, an organic co-solvent and a macromolecular compound.
Solution polymerized vinyl halide resins have been widely used as an interior coating resin for the beer and beverage cans. They are FDA approved vehicles, provide good protection for the metallic substrates from corrosive effects of the contents, and excellent blush resistance during pasteurization while contributing no undesirable taste properties. For these reasons, they are preferred over most of the other coating resins for this demanding application.
Because these vinyl halide resins are normally applied as a lacquer, a large amount of organic solvents is evolved during the application. Being ecologically undesirable and expensive, this technology has been replaced rapidly by other technologies where the solvent requirement can be reduced to a much lower level. The most prominent one is the waterborne coatings technology.
A waterborne coating may be formed from a water-soluble resin, a latex, or an emulsion. A water-soluble resin formulation is often too water sensitive to pass the required blush resistance test. On the other hand, latices and emulsions produced by the conventional methods almost always contain one or a combination of surfactants to effect the dispersion as well as fragments from the initiator system used. These additives often become a source of either poor blush resistance or possibly bad taste properties, or both.
It is therefore an object of this invention to prepare water-borne colloidal dispersions of vinyl resins suited for various coating applications.